1. Field of the Invention
This invention is applicable to a public telephone network. This invention is applicable to communications by means of a telephone set which is handy, of pocket-size, and transportable when carried by a user. This invention more particularly is related to a communication system wherein a subscriber of a public telephone network carries with him/her a telephone when he/she travels, and when a call to the personal telephone number is generated in the network, connection is automatically made with the telephone set carried by him/her.
2. Description of the Prior Art
In the prior art public telephone network, a subscriber's line is wired from the subscriber's switch, and one subscriber number is usually assigned to a subscriber's line except for special cases. Calls for connection are made in the network by the number and controlled to be connected with the line thereof. The connection of calls made from inside of the telephone network and destined to the subscriber's line is made irrespective of the telephone type connected to the line so far as the telephone satisfies the standard conditions of the network.
There has been widely used a cordless telephone or an automobile telephone which can make or receive a call from an arbitrary location to or from a telephone within the public telecommunication network by means of a small, handy and movable telephone. The automobile telephone system using a relatively small portable type telephone has recently become popular.
There has been proposed a system wherein a user uses an IC card on which his/her telephone number and/or personal information are written in, and when the user inserts the card at a terminal within a public telecommunication network, he/she can use the terminal as the personal telephone.
In Germany, a service has already been put into practice which connects a call from a small movable telephone via an automobile station when an ID card is mounted on the telephone.
In the personal communication system where users are individuals, it is ideal that an individual user is assigned with a subscriber's number, and when a call for connection is made to the number, the connection is made with the person no matter where he/she is. The personal user herein means not only the person specified by personal name but a person specified by the business section of an organization.
The above-mentioned cordless or automobile telephone has satisfied conditions for the optimal modes of such a dream telephone to a certain extent. However, no matter how conveniently portable the cordless telephones are, their use is limited principally within a building due to the limitation of received power, and cannot be extended beyond such an area. Automobile telephones including those designed as portable inevitably require much power in transmission as the scope of coverage by a base station is designed to be wide. It therefore needs a large and heavy battery, making the telephone bulky in size and inconvenient. As available radio frequencies are limited, all the connections requested by personal subscribers (on the order of several millions) cannot be accommodated within a public telephone network. As the human living environment becomes increasingly diverse, the network should be extended to inside of buildings, basements, or construction sites where radio waves cannot easily reach. It would be impossible to build such an extensive system only with radio waves.
Telephone sets are indispensable tools we use in everyday life in modern society, and we are particular about their color, design, form, performance and price. We want to have a wide choice when purchasing them. Some wish to change their telephone sets by the season or by their preference occasionally. Some even wish to use different sets daily. Telephone sets might sometimes be gift items. Some exchange their sets with friends.
Telephone manufacturers hope to design and manufacture various types of telephone sets to meet such diversified demands of users and to sell newly designed sets which go with the mode of fashion. They also want to introduce advanced technology in their products.
Reflecting such trends, various types of telephone sets are currently available at retail electric appliance shops or big department stores. In the days when one subscriber's number corresponded to one subscriber's line in a one-to-one relationship, a user bought a telephone and simply connected it to the terminal of his/her subscriber's line. However, as we can travel with our personal telephones nowadays, if subscribers are given different numbers whenever they purchase or change their telephone set, it would be extremely troublesome as they must provide their new numbers to their friends or business acquaintances. If we change telephone sets without changing the subscriber's number just like the prior art automobile telephone, we would have to bring the new set to a central telephone office for setting a new number for it every time we get a new one, causing great trouble.